I've no desire to get embroiled in the software wars, but it should be pointed out that after many years of neglect MS has finally started moving on the virus/spyware threat. Insiders say they have declared war on the malware writers, and MS is doling out a lot of bucks to back up the effort.
So, for a while at least, I'll withhold judgement until I see how well they do. They certainly have the resources, so hopefully some good will come of this.
On my original WD question. I joined that MS reporting network, and the very same evening it reported a trojan to be zapped. I have nothing to be unhappy over so far.